Transcript ppt
The Ordered Universe The Birth of Modern Astronomy (Trefil & Hazen, The Sciences, Ch 2) Homer’s “Bear that never bathes” Stonehenge …one of several old “time-reckoning” machines. It’s moving parts are in the sky. Ancient astronomy Great Pyramid of Giza …was aligned to the pole star, and it was possible to read the seasons from the position of the pyramid’s shadow. The Mayans of Yucatan …inscribed stone monuments with formulae for predicting solar eclipses Plains Indians • Recorded the rising points of the bright stars, to record seasonal grazing patterns. Political Power …Columbus influenced native people to provide food for his crew by warning of “an inflamed and angry moon.” Brief Overview of Early Science • Greece, 4th C B.C. • Roman Empire Fell, 5th C A.D. • Chinese, Polynesians, Arabs • Islamic influences in Spain 10-12th C • Universities emerge in Europe, 13th C • Printing press, 15th C • Copernican hypothesis heliocentrism 15th C • Galileo and “scientific method” 17th C The Ordered Universe Part 1: Ancient Astronomers Ancient China • Working calendar 13th Century B.C.! • Star Catalog with 800 entries, 350 B.C.! • Observed comets and supernovas Babylonian Astronomy • Oldest scientific documents • 800 B.C. • Record eclipses, positions of planets and rise/setting of the Moon Greek Astronomy 600 B.C. to 200 A.D. • Thales introduced geometrical ideas into astronomy. • Pythagorus universe as a series of concentric spheres • Eudoxus the idea of rotating spheres to account for the observed complexities of planetary motions. • Aristotle correct explanation of lunar eclipses; sound argument for the spherical shape of the earth. Astronomy at Alexandria 3rd Century B.C. • Aristarchus • Determined size and distance of Sun and Moon rel to Earth • Developed 1st heliocentric model • Eratosthenes • Made accurate calculation of the size of the Earth Claudius Ptolemy • Greek astronomer from 2nd Century, proposed first enduring theory of the universe, an Earth-centered or Geo-centric model. Occam’s Razor and interpreting oddities • 14th Century English Philosopher • Given a choice, the simplest solution to a problem is most likely to be right. Stonehenge The Ordered Universe Part 2: Birth of Modern Astronomy The “Fab. Four” Copernicus, Brahe, Kepler, Galileo (a) (b) Figure 2-5 The Ptolemaic (a) and Copernican (b) systems both assumed that all orbits are circular. The fundamental difference is that Copernicus placed the Sun at the center. Mikolai Kopernik, 1473 • Copernicus outlined a theory for a sun-centered or “heliocentric” universe • 1543, On the Revolutions of the Spheres Tycho Brahe,1546-1601 Johannes Kepler, 1571-1630 Kepler’s Laws • Planets orbit the sun in an ellipse. • planets move more rapidly when close to the sun and more slowly when distant from the sun • The cube of the mean distance of each planet from the sun is proportional to the square of the time it takes to complete one orbit Check your neighbor… • Summarize key ideas of our attempt to make sense of the universe – – – – – – – Ancients of China, Egypt, Greece Aristarchus Eratosthenes Ptolemy Copernicus Brahe Kepler